One conventional system for controlling the temperature and humidity of the air introduced into the work space in an air conditioned plant consists of reducing the temperature of the air introduced into the work area to a temperature corresponding to the wet bulb temperature desired in the space, saturating the air with moisture at that temperature, and thereafter adding sensible heat to the air so as to elevate the temperature to the dry bulb temperature desired in the space. While such a method facilitates the control of the humidity of the air entering the conditioned space, it uses unnecessary energy when it is necessary to first cool the air to a temperature corresponding to the wet bulb temperature and thereafter reheat the air.
In order to conserve energy, it has been proposed to control the dry bulb temperature and humidity of the air by controlling the temperature of the spray used to wash the air and the quantity of the water used in the spray. For example, see U.S. Pat. No. 4,098,666 in which the air is reconditioned as set forth above and then split into separate flows to treat work material, in this instance tobacco, in two sequential stages.